The word bastan is the present form of bastar in the third person plural.
See the full bastar conjugation

bastar

Estas medidas son fundamentales pero, por sí solas, no bastan.
These steps are essential but, alone, they are not sufficient.
Dos horas bastan para confirmar la importancia de esta entrevista.
Even two hours are enough to confirm the importance of this conversation.
Hemos de reconocer que estas normas comunes mínimas no bastan.
We need to recognise that these minimum common rules are not sufficient.
Estos puntos bastan para que yo vote a favor.
These points were sufficient for me to vote in favour.
Al mismo tiempo, las iniciativas nacionales no bastan por sí solas.
At the same time, national efforts alone are not sufficient.
Las contribuciones de las misiones por sí solas no bastan.
The contributions of missions alone are not sufficient.
Señor Szymánski, el agua y medicamentos por sí solos no bastan.
Mr Szymánski, water and medicines alone are just not enough.
No necesitamos sus casas, los bosques nos bastan.
We don't need their houses, the woods are just fine.
Las cereales no bastan para el consumo de la isla.
The cereals produced on the island are insufficient for consumption.
Los elevados ideales y las expresiones de buena voluntad no bastan.
Lofty ideals and expressions of goodwill are not enough.
Las cifras macroeconómicas no bastan para ocultar la realidad.
The macroeconomic data are not enough to hide reality.
Las palabras no bastan, de todos nosotros se esperan hechos.
Words do not suffice; deeds are expected from us all.
Y a veces te encuentras preguntándote si las buenas intenciones bastan.
And sometimes you get to wondering if good intentions are enough.
A veces dos ojos no bastan, y necesitan ayuda.
Sometime two eyes aren't enough, when you need help.
Al mismo tiempo, estas listas no bastan.
At the same time, these lists are still not enough.
Las declaraciones de buenas intenciones son loables, pero no bastan.
Declaring good intentions is laudable, but it is not enough.
Por tanto, los imanes pequeños y baratos bastan para activar el CI.
Therefore, small and inexpensive magnets are sufficient to trigger the IC.
Pero los sentimientos místicos por sí solos no le bastan.
But mystical feelings alone are not sufficient for you.
Es evidente que las buenas palabras no bastan.
It is obvious that fine words alone are not enough.
En este campo, la buena voluntad, el amor mismo, no bastan.
In this field, goodwill, love itself, are not sufficient.
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